Removal of spray residue



Patented Jan. 18, 1938 PATENT OFFICE REMOVAL OF SPRAY RESIDUE Harry G.McLean and Albert L. Weber, New Brunswick, N. J., assignors to EndowmentFoundation, New Brunswick,

tion of New Jersey N. J., a corpora.-

No Drawing. Application May 27, 1935,

Serial No. 23,707

3 Claims.

This invention relates to the washing of fruits and vegetables, such asapples, pears, string beans, peas, lettuce and the like to remove spraymaterials from the surface thereof.

More particularly, the present invention is directed'to the removal ofarsenic or lead compounds which may be associated with mineral oils andwhich have been used in various combinations for spraying fruit trees toeradicate cer- 10 tain insect pests. The invention is also applicable towaxy fruit and the like in which the spray residues have become embeddedin the wax, and

which may not have been oil sprayed. Recently the Government has loweredthe tolerance on the content of both arsenic and lead on fruit foredible purposes so that it has become increasingly essential that awashing operation be conducted to effectively remove these materials.Where a mineral oil has been used for spraying l purposes it maystimulate the formation of a resistant waxy covering on the fruit whichprevents the ready access of the washing solution and thus tendstoprevent effective cleaning of the fruit and removal of the lead andarsenic.

25 A. number of methods for washing sprayed fruit have been developedand used. These have been onlyindiiferently successful and have notalways served to bring the arsenic and lead content down 'below therelatively small amount allowed by the Government. One of theseprocesses consisted in providing a solution of hydrochloric acid with anemulsion of kerosene. The solution was heated to aboutl00 F. andthefruit washed therein. This process was unable to remove the 55'arsenicalresidue sufiiciently from fruit sprayed with mineral oil, fishoil or fish oil soaps, and lead arsenate to meet the export or thedomestic market requirements. I

Another previously proposed process consisted in first dipping the fruitin methyl alcohol solution to remove the coatings of oil or wax whichformon the fruit, after which the fruit was subjected to a cleaningoperation with hydrochloric acid solution. This process offered seriousdifli- 5 culties in that it was necessary to conduct two separatewashing operations which greatly increased the cost of processingbecause of the need for maintaining additional washing equipment. Themethyl alcohol may have detrimental effects on the health of the workerswhich is caused by prolonged exposure to the alcoholic vapors.

Still another process of the prior art resided in the use of suchdetergents as trisodium phosphate, sodium carbonate or sodium silicatein solution for washing fruit and the like. These substances do notremove the lead from the fruit to a satisfactory degree in all cases,and the solutions must be heated, say to 90-100 F., in order to makethem at all effective.

The present invention is directed to the washing of fruit with asolution which is comparatively inexpensive and which is capable ofefiectively removing the arsenical and lead residues from lead arsenateand oil sprayed fruit.

It is among the objects of our invention to provide a. solution forwashing fruit which is noninfiammable in nature, which in no waydetrimentally aifects the keeping qualities or appearance of the fruit,which has a sufiiciently high solvent action so that without thenecessity of applying heat it will remove the undesirable residues fromthe fruit, which will in no way endanger the health of the workers, andwhich is suitable for use with either the homemade flotation washers anddipping tanks, or for use with the various types of commercial washingmachines in which a short period of contact between the fruit and thewashing solution is maintained.

In practicing our invention, we provide a. water solution of an acid,preferably a mineral acid, such as hydrochloric, nitric or the like,although for practical purposes hydrochloric acid has been foundextremely well suited. The amount of hydrochloric acid in solution isgenerally not over three percent and usually is from 1 to 2 percent byweight. In some cases up to 5% of the HCl may be used. To this solution,we add a degumming or wetting agent of the type which is made by thesulphonation of the higher aliphatic alcohols, the higher aliphatichydrocarbons and aromatic compounds such as aromatic hydrocarbons,phenols and the like, including complexes of sulphonated aromaticcompounds with aliphatic acids. The higher aliphatic hydrocarbons andthe aromatic compounds contain at least six carbon atoms. Usually thesulphonic compound, which is termed a sulphonic acid, is neutralized soas to form an alkali metal salt thereof. The preparation of suchsubstances is well known and need not be here described.

While we are enabled to use substantially all of the degumming agents ofthe above described types, we have found that the sulphonatedaromaticand hydroaromatic compounds are particularly effective in the form oftheir alkali metal salts. Among such compounds are the sodiumsalts ofthe butyl and propyl naphthalene sulphonic acids sodium salt of abietenesulphonic acid, sodium cresyl' stearo sulphonate, sodium toluol stearosulphonate, sodium paratertiaryamylphenol stearo sulphonate, sodiumcymene stearo sulphonate, sodium carvacrol stearo sulphonate and thesodium salt of alkylated hydroxy diphenyl sulphonic acid such as thebutylated or propylated compounds. The corresponding salts of alkylateddiphenyl sulphonic acids are also useful but not quite as powerful. -Thesodium isopropyl and secondary butyl' naphthalene sulphonates haveproven to be highly effective and, because of their low price,constitute the preferred degumming agents for use in the presentinvention. We have foundthat in conjunction with the degumming agent, ifthere is present a substantial proportion of a water soluble salt suchas ammonium chloride, sodium chloride, or sodium sulphate, increasedeffectiveness in the resultant operation is obtained. Of the aliphaticcompounds, the best results were obtained with sulphuric ester of laurylalcohol.

A solution of the above described type is very efiective in the removalof the arsenical residue, but we have found that in washing apparatushaving positive agitation, considerable foaming takes place which mayresult in over-flowing of the froth from the apparatus and thus resultin the loss of washing solution. To overcome this, we generally and tothe solution a substance which is adapted to prevent the foaming. Whilea considerable number of substances of various types may be used forthis purpose we find that substances taken fromthe following class,aliphatic ketones and alcohols having from 6 to 10 carbon atoms, pineoil, fusel oil, degras, naphtha or mixtures thereof, usually incomparatively small amounts, produce the desired anti-foaming effects. i

The washing solutions may vary greatly in the composition thereof. Asindicated above the amount of hydrochloric acid should ordinarily be notover three percent and is usually from 1 to 2 percent by weight. Theamount of the degumming agent is usually not over 2 percent andordinarily from A; to 1 percent or even'less, has

been found suitable for the purpose. When a soluble salt is used inconjunction withthe degumming agent, it is not necessary to use morethan about 1 to 2 percent thereof. A consider ably smaller proportion ofantifoaming substance is required and ordinarily we use not-over .5%

cases it is unnecessary to heat the solutions,

which was considered essential in prior processes. The washing operationmay be conducted for any desired length of time such as is usual infruit washing. For instance, in the spray and flood type of washingmachines the fruit may be held in contact with theacid solution forabout V to 1 minute. In the commercial type of washer heating to 100r'fior a short time assists'in the removal of spray residues in ashorter time but heating is not at all essential. With the homemadeflotation type of washing machine the period of contact may be on theaverage about 3 minutes followed by thorough rinsing in water.

Repeated tests on fruit which had been sub jected to this process, andwhich had been safely,

sprayed with lead arsenate and calcium caseinate or with lead arsenateand petroleum oil, have shown that the rated capacity of the washingmachines is very materially increased bythe use of a degumming orwetting agent as disclosed herein, due to the rapid and effectivecontact established between the hydrochloric acid and the lead arsenate.This is probably due to the rapid removal from the surface of the fruitof the oil or the outer film of the wax in which the spray residues areembedded, allowing the hydrochloric acid to make direct contact with thelead arsenate and dissolve the same. By the use of this invention, thewashed fruit shows no deleterious effects after long storage and thesurface of the fruit is bright and clear.

Although we have described our invention setting forth the generalnature thereof and indicating the various materials. and proportionswhich have been found adapted for commercial practice, it is toice-understood that our invention is not limited to the detailsdescribed herein. It will be apparent to those skilled in the art thatvariations in the strength of solutions, in the time of contact of thefruit with the solutions, and the type and character of the apparatusused for washing, may be madeat will with good results.

'I'he'character and the amount of spray, as well as the length ofstorage of the fruit prior to the washing operation, may necessitatewide variations in the composition of the washing solutions and in thetimes of treatment. These and other changes are considered to be withinthe scope of this invention which is not to be limited except by theclaims appended hereto.

-We claim:

1. A method of washing fruit and the like to remove spray materials fromthe surface thereof which includes applying to the fruit a solutioncontaining a small proportion of hydrochloric acid and an alkali metalsalt of a sulphonated phenol compound.

2. A method of washing fruit and the like'to remove spray materials fromthe surface thereof which includes applying to the fruit 9.. solutioncontaining a small proportion of hydrochloric acid and an alkali metalsalt of an aromatic stearo sulphonate.

3. A method or washing fruit and ,the' like to remove spray materialsfrom the surface thereof which includes applying to the fruit a solutioncontaininga small proportion of hydrochloric.

acid and analkall metal salt of a cresyl stearo sulphonate.

. [HARRY c. MoLEAN. .ALBERT L. WEBER.

